Electric Train Demonstrator

If you ever want to pique a kid’s interest in technology, it is best to bring out something simple, yet cool. There was a time that showing a kid how a crystal radio could pull in a radio station from all the way across town fit the bill. Now, that’s a yawner as the kid probably carries a high-tech cell phone with a formidable radio already. Your latest FPGA project is probably too complicated to grasp, and your Arduino capacitance meter is–no offense–too boring to meet the cool factor criterion.

There’s an old school project usually called an “electromagnetic train” that works well (Ohio State has a good write up about it as a PDF file). You coil some bare copper wire around a tubular form to make a tunnel. Then a AAA battery with some magnets make the train. When you put the train in the tunnel, the magnetic forces propel the train through the tunnel. Well, either that or it shoots it out. If that happens, turn the train around and try again. There’s a few of these in Internet videos and you can see one of them (from [BeardedScienceGuy]) below.

This isn’t a new idea, but the Ohio State instructions are well suited for use in a classroom or just to work with an intellectually curious kid. Since this is simple enough, you can work with the kids (or kid) to actually build the device or let them build several in groups.

Our company used to make parts which utilized neodymium magnets. The magnets came in uncharged, we installed them and charged them. The magnets themselves were very small, about half inch by half inch, maybe 1/8 inch thick. We built a prototype charger, which simply consisted of stepping up the voltage, rectify, charge a large bank of capacitors and a very large SCR to dump the charge into a coil. This was NOT your daddy’s DC power supply. The parts we used rated in the hundreds of amps….
The first prototype charger we used a large piece of PVC pipe (probably 3 inch diameter) and wound copper tubing around. The copper tubing had a fiberglass sleeving installed on it as an insulator prior to winding, could have been anything, that was what we had at first. I still remember the look on the faces of people while we rigged up the lathe as a coil winder. We basically grabbed what we had and threw it all together because the beancounters wouldn’t allow a budget at the beginning but wanted to be making a product on some ungodly time scale!
We could easily put any metal slug in it, say a large bolt or nut, and shoot it across the lab.
After that we had to go outside, dragging frankencharger on wheels, to do further testing. We had to buy and build a special water cooling system to run water through the tubing because, duh, dumping several hundred amps into a copper coil numerous times made it hot.
Magnet charging isn’t special, but one has to make sure it is fully charged…..

By the end, we could shoot metal slugs over the two story roof and into the front parking lot, where many of the bean counters and managers parked.
Nothing intentional, just an added perk.

This prototype is still around, it worked as a few years ago, though we changed the charge coil for charging magnets. Much, much more concentrated magnetic field.

Another thing about strong magnetic fields, they can pass through walls. So, for all you computer geeks who seem to have that arrogant, I am God attitude, a well placed coil on the other side of the wall of a server room will cause hard drives to crash and erase data. It will also play hell with electronics, especially relay coils…..might want to think twice of who you talk down to next time youre assistance is required…..

Won’t work—this needs lots of power. My go-to for dying batteries was (before I switched to Eneloops) cheap flashlights scattered around anywhere I thought I might need one. Sometimes a few minutes of dim light is all you need.

Unless it welds itself down, I’d assume you’d have an extra ohm in circuit from 2 points of shitty contact, gets stuck, it has the potential to weld in place lose some of that resistance, and thus more rapidly discharge the battery.

Trying to post a link to a site with wonderful info on this project, but it isn’t working (Al, do you hate me for some reason?). So, just search for “wayne schmidt this and that” and scroll down to find the “simplest train” link. Be sure to watch both videos!

“There was a time that showing a kid how a crystal radio could pull in a radio station from all the way across town fit the bill. Now, that’s a yawner as the kid probably carries a high-tech cell phone with a formidable radio already.”

Pocket sized transistor radios are a lot older than I am. I remember thinking the lack of a power source was impressive when I was a kid.

I’d like to see some snot nosed kid with a cellphone go without a charger!